Process for producing mixture of dihydroxydiphenylsulfone isomers

ABSTRACT

The present invention provides a process for producing a mixture of dihydroxydiphenylsulfone isomers containing 2,4′-dihydroxydiphenylsulfone, the process comprising heating 4,4′-dihydroxydiphenylsulfone or a mixture of dihydroxydiphenylsulfone isomers containing at least 85 wt. % of 4,4′-dihydroxydiphenylsulfone in the presence of phenol and sulfuric or sulfonic acid.

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application PCT/JP02/09920, filed Sep. 26, 2002, whichclaims priority to Japanese Patent Application No. 2001-300933, filedSep. 28, 2001, and Japanese Patent Application No. 2001-300942, filedSep. 28, 2001. The International Application was not published under PCTArticle 21(2) in English.

TECHNICAL FIELD

The present invention relates to a process for producing a mixture ofdihydroxydiphenylsulfone isomers containing2,4′-dihydroxydiphenylsulfone.

BACKGROUND ART

Among various phenolic compounds, 2,4′-dihydroxydiphenylsulfone(hereinafter occasionally referred to as 2,4′-DDS) has recentlyattracted attention because of its great utility as a color developerfor heat-sensitive paper.

Known methods for producing 2,4′-DDS include the separation andpurification of 2,4′-DDS from mixtures containing 2,4′-DDS and4,4′-dihydroxydiphenylsulfone (hereinafter occasionally referred to as4,4′-DDS).

Moreover, it is known that when 4,4′-DDS is heated in a phenol solventin the presence of an acid catalyst, isomerization occurs, therebyproducing a mixture of dihydroxydiphenylsulfone isomers containing4,4′-DDS and 2,4′-DDS in a weight ratio of about 75 to about 25(isomerization equilibrium) (Journal of the Chemical Society of Japan,1985 (1), 70–74). However, since this isomerization reaction requires 20hours or longer to reach isomerization equilibrium even under heatingconditions of 190° C. or higher, it is difficult to employ thisisomerization reaction industrially.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a process for producing amixture of dihydroxydiphenylsulfone isomers containing an enhancedamount of 2,4′-DDS, the process being able to induce isomerizationequilibrium in a short period of time when 4,4′-DDS is isomerized.

Other objects and characteristics of the present invention will becomeevident by the disclosure provided hereinbelow.

The inventors conducted extensive research and found that heating4,4′-DDS in the presence of specific amounts of phenol and sulfuric acidcan induce isomerization equilibrium in a short period of time. Thepresent invention has been accomplished based on this finding.

Furthermore, the inventors found that heating 4,4′-DDS in the presenceof phenol and sulfonic acid can induce isomerization equilibrium in ashort period of time. The present invention has been accomplished basedalso on this finding.

In other words, the present invention provides processes for producing amixture of dihydroxydiphenylsulfone isomers as described below:

-   -   1. A process for producing a mixture of dihydroxydiphenylsulfone        isomers containing 2,4′-dihydroxydiphenylsulfone, the process        comprising heating 4,4′-dihydroxydiphenylsulfone to a        temperature of 160° C. or higher in the presence of an equal        weight or less of phenol and 20 mol % or less of sulfuric acid        relative to the 4,4′-dihydroxydiphenylsulfone.    -   2. A process for producing a mixture of dihydroxydiphenylsulfone        isomers containing 2,4′-dihydroxydiphenylsulfone, the process        comprising heating a mixture of dihydroxydiphenylsulfone isomers        containing 4,4′-dihydroxydiphenylsulfone in a proportion of at        least 85 wt. % to a temperature of 160° C. or higher in the        presence of an equal weight or less of phenol and 20 mol % or        less of sulfuric acid relative to the mixture.    -   3. A process for producing a mixture of dihydroxydiphenylsulfone        isomers containing 2,4′-dihydroxydiphenylsulfone, the process        comprising heating 4,4′-dihydroxydiphenylsulfone in the presence        of phenol and sulfonic acid.    -   4. A process for producing a mixture of dihydroxydiphenylsulfone        isomers containing 2,4′-dihydroxydiphenylsulfone, the process        comprising heating a mixture of dihydroxydiphenylsulfone isomers        containing 4,4′-dihydroxydiphenylsulfone in a proportion of at        least 85 wt. % in the presence of phenol and sulfonic acid.

Hereinbelow, the process for producing a mixture ofdihydroxydiphenylsulfone isomers of the present invention is describedin more detail:

[Process Employing Sulfuric Acid]

As a single starting material of the present invention, 4,4′-DDS mayhave a purity of 99% or higher.

A mixture of dihydroxydiphenylsulfone isomers containing 4,4′-DDS in aproportion of at least 85 wt. % can also be used as a starting material.It is preferable that this isomeric mixture contains 2,4′-DDS as anotherisomer.

The starting material, i.e., 4,4′-DDS or a mixture ofdihydroxydiphenylsulfone isomers containing 4,4′-DDS in a proportion ofat least 85 wt. %, is isomerized by heating in the presence of phenoland sulfuric acid.

Phenol is used in a weight equal to or less than, and preferably in aweight of 0.1 to 0.8 times as much as, the starting material, i.e.,4,4′-DDS or a mixture of dihydroxydiphenylsulfone isomers containing4,4′-DDS.

Sulfuric acid is used in a proportion of 20 mol % or less, andpreferably in a proportion of 1 to 10 mol %, based on the startingmaterial, i.e., 4,4′-DDS or a mixture of dihydroxydiphenylsulfoneisomers containing 4,4′-DDS.

Solvents may or may not be used. When solvents are used, heat- andacid-resistant solvents such as sulfolane and the like are preferable.

The reaction temperature for conducting isomerization is 160° C. orhigher, and preferably 170 to 210° C. Isomerization can be conductedunder pressure as necessary.

The reaction time is not limited. The reaction may be continued untilisomerization equilibrium. The preferable reaction time is 0.1 to 15hours, and more preferable is 0.5 to 10 hours.

The desired product of the present invention, i.e., a mixture ofdihydroxydiphenylsulfone isomers containing 2,4′-DDS, is primarilycomposed of 4,4′-DDS and 2,4′-DDS. Preferable is a mixture containing2,4′-DDS in a proportion of 15 to 30 wt. %, more preferable is a mixturecontaining 2,4′-DDS in a proportion of 20 to 30 wt. %, and especiallypreferable is a mixture containing 2,4′-DDS in a proportion of 22 to 30wt. %.

2,4′-DDS can be separated from a mixture of dihydroxydiphenylsulfoneisomers containing 2,4′-DDS produced according to the invention usingknown separation and purification methods.

According to the process of the present invention, when 4,4′-DDS isisomerized, isomerization equilibrium is achieved in a short period oftime, and a mixture of dihydroxydiphenylsulfone isomers containing anenhanced amount of 2,4′-DDS can be obtained.

[Process Employing Sulfonic Acid]

As a single starting material of the present invention, 4,4′-DDS mayhave a purity of 99% or higher.

A mixture of dihydroxydiphenylsulfone isomers containing 4,4′-DDS in aproportion of at least 85 wt. % can also be used as a starting material.It is preferable that this isomeric mixture contains 2,4′-DDS as anotherisomer.

The starting material, i.e., 4,4′-DDS or a mixture ofdihydroxydiphenylsulfone isomers containing 4,4′-DDS in a proportion ofat least 85 wt. %, is isomerized by heating in the presence of phenoland sulfonic acid.

Phenol is used preferably in a weight twice as much as or less than, andmore preferably in a weight 0.1 to 1 times as much as, the startingmaterial, i.e., 4,4′-DDS or a mixture of dihydroxydiphenylsulfoneisomers containing 4,4′-DDS.

Examples of sulfonic acids usable in the invention includebenzenetrisulfonic acid, benzenedisulfonic acid, chlorobenzenedisulfonicacid, toluenesulfonic acid, phenolsulfonic acid, and like aromaticmono-, di-, or trisulfonic acids; methanesulfonic acid, ethanesulfonicacid, trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, andlike optionally-fluorinated aliphatic sulfonic acids; Nafion® and likepolymeric sulfonic acids; etc. Among these sulfonic acids, aromaticmono-, di-, or trisulfonic acids are preferable; and benzenedisulfonicacid, toluenesulfonic acid, and the like are more preferable.

Sulfonic acid is used preferably in a proportion of 20 mol % or lower,and more preferably in a proportion of 1 to 10 mol %, based on thestarting material, i.e., 4,4′-DDS or a mixture ofdihydroxydiphenylsulfone isomers containing 4,4′-DDS.

Solvents may or may not be used. When solvents are used, heat- andacid-resistant solvents such as sulfolane and the like are preferable.

The reaction temperature for conducting isomerization is preferably 160°C. or higher, and more preferably 170 to 210° C. Isomerization can beconducted under pressure as necessary.

The reaction time is not limited. The reaction may be continued untilisomerization equilibrium. The preferable reaction time is 0.1 to 15hours, and more preferable is 0.5 to 10 hours.

The desired product of the present invention, i.e., a mixture ofdihydroxydiphenylsulfone isomers containing 2,4′-DDS, is primarilycomposed of 4,4′-DDS and 2,4′-DDS. Preferable is a mixture containing2,4′-DDS in a proportion of 15 to 30 wt. %, more preferable is a mixturecontaining 2,4′-DDS in a proportion of 20 to 30 wt. %, and especiallypreferable is a mixture containing 2,4′-DDS in a proportion of 22 to 30wt. %.

2,4′-DDS can be separated from a mixture of dihydroxydiphenylsulfoneisomers containing 2,4′-DDS produced according to the invention usingknown separation and purification methods.

According to the process of the present invention, when 4,4′-DDS isisomerized, isomerization equilibrium is achieved in a short period oftime, and a mixture of dihydroxydiphenylsulfone isomers containing anenhanced amount of 2,4′-DDS can be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

Examples are given below to illustrate the invention in more detail.

EXAMPLE I-1

To 100 g (0.4 mol) of dihydroxydiphenylsulfone (containing 4,4′-DDS in aproportion of 99.8 wt. % and 2,4′-DDS in a proportion of 0.1 wt. %;hereinafter referred to as bisphenol S (1)) were added 50 g of phenoland 1.6 g (0.016 mol, 4 mol % relative to bisphenol S (1)) of 98%sulfuric acid. The mixture was heated to 195° C. and stirred at thistemperature. The results of HPLC (high performance liquidchromatography) analysis conducted after 2 hours of stirring revealedthat the mixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of85:15, and the mixture after 6 hours of stirring contained 4,4′-DDS and2,4′-DDS in a weight ratio of 76:24.

EXAMPLE I-2

To 100 g of bisphenol S (1) were added 50 g of phenol and 4 g (0.04 mol,10 mol % relative to bisphenol S (1)) of 98% sulfuric acid. The mixturewas heated to 180° C. and stirred at this temperature. The results ofHPLC analysis conducted after 2 hours of stirring revealed that themixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of 86:14, andthe mixture after 6 hours of stirring contained 4,4′-DDS and 2,4′-DDS ina weight ratio of 76:24.

EXAMPLE I-3

To 100 g of bisphenol S (1) were added 50 g of phenol and 4 g (0.04 mol,10 mol % relative to bisphenol S (1)) of 98% sulfuric acid. The mixturewas heated to 210° C. and stirred at this temperature. The results ofHPLC analysis conducted after 1 hour of stirring revealed that themixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of 75:25, andthe mixture after 2 hours of stirring contained 4,4′-DDS and 2,4′-DDS ina weight ratio of 73:27.

EXAMPLE I-4

To 100 g (0.4 mol) of dihydroxydiphenylsulfone (containing 4,4′-DDS in aproportion of 86 wt. % and 2,4′-DDS in a proportion of 14 wt. %;hereinafter referred to as bisphenol S (2)) were added 50 g of phenoland 1.6 g (0.016 mol, 4 mol % relative to bisphenol S (2)) of 98%sulfuric acid. The mixture was heated to 195° C. and stirred at thistemperature. The results of HPLC analysis conducted after 2 hours ofstirring revealed that the mixture contained 4,4′-DDS and 2,4′-DDS in aweight ratio of 79:21, and the mixture after 6 hours of stirringcontained 4,4′-DDS and 2,4′-DDS in a weight ratio of 75:25.

COMPARATIVE EXAMPLE I-1

To 15 g (0.06 mol) of bisphenol S (1) were added 36 g of phenol and 3 g(0.03 mol, 50 mol % relative to bisphenol S (1)) of 98% sulfuric acid.The mixture was heated to 195° C. and stirred at this temperature. Theresults of HPLC analysis conducted after 2 hours of stirring revealedthat the mixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of88:12, the mixture after 6 hours of stirring contained 4,4′-DDS and2,4′-DDS in a weight ratio of 82:18, and the mixture after 20 hours ofstirring contained 4,4′-DDS and 2,4′-DDS in a weight ratio of 78:22.

EXAMPLE II-1

To 100 g (0.4 mol) of bisphenol S (1) were added 100 g of phenol and 5 g(0.02 mol, 5 mol % relative to bisphenol S (1)) of benzenedisulfonicacid. The mixture was heated to 180° C. and stirred at this temperature.The results of HPLC analysis conducted after 2 hours of stirringrevealed that the mixture contained 4,4′-DDS and 2,4′-DDS in a weightratio of 81:19, and the mixture after 6 hours of stirring contained4,4′-DDS and 2,4′-DDS in a weight ratio of 77:23.

EXAMPLE II-2

To 100 g of bisphenol S (1) were added 50 g of phenol and 3 g (0.017mol, 4 mol % relative to bisphenol S (1)) of toluenesulfonic acid. Themixture was heated to 195° C. and stirred at this temperature. Theresults of HPLC analysis conducted after 2 hours of stirring revealedthat the mixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of79:21, and the mixture after 6 hours of stirring contained 4,4′-DDS and2,4′-DDS in a weight ratio of 75:25.

EXAMPLE II-3

To 100 g of bisphenol S (1) were added 50 g of phenol and 6.9 g (0.04mol, 10 mol % relative to bisphenol S (1)) of toluenesulfonic acid. Themixture was heated to 180° C. and stirred at this temperature. Theresults of HPLC analysis conducted after 2 hours of stirring revealedthat the mixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of86:14, and the mixture after 6 hours of stirring contained 4;4′-DDS and2,4′-DDS in a weight ratio of 76:24.

EXAMPLE II-4

To 100 g of bisphenol S (1) were added 50 g of phenol and 6.9 g (0.04mol, 10 mol % relative to bisphenol S (1)) of toluenesulfonic acid. Themixture was heated to 210° C. and stirred at this temperature. Theresults of HPLC analysis conducted after 1 hour of stirring revealedthat the mixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of75:25, and the mixture after 2 hours of stirring contained 4,4′-DDS and2,4′-DDS in a weight ratio Of 73:27.

EXAMPLE II-5

To 100 g (0.4 mol) of bisphenol S (2) were added 50 g of phenol and 3 g(0.017 mol, 4 mol % relative to bisphenol S (2)) of toluenesulfonicacid. The mixture was heated to 195° C. and stirred at this temperature.The results of HPLC analysis conducted after 2 hours of stirringrevealed that the mixture contained 4,4′-DDS and 2,4′-DDS in a weightratio of 77:23, and the mixture after 6 hours of stirring contained4,4′-DDS and 2,4′-DDS in a weight ratio of 75:25.

COMPARATIVE EXAMPLE II-1

To 15 g (0.06 mol) of bisphenol S (1) were added 36 g of phenol and 3 g(0.03 mol, 50 mol % relative to bisphenol S (1)) of 98% sulfuric acid.The mixture was heated to 195° C. and stirred at this temperature. Theresults of HPLC analysis conducted after 2 hours of stirring revealedthat the mixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of88:12, the mixture after 6 hours of stirring contained 4,4′-DDS and2,4′-DDS in a weight ratio of 82:18, and the mixture after 20 hours ofstirring contained 4,4′-DDS and 2,4′-DDS in a weight ratio of 78:22.

1. A process for producing a mixture of dihydroxydiphenylsulfone isomerscontaining 2,4′-dihydroxydiphenylsulfone, the process comprising heating4,4′-dihydroxydiphenylsulfone to a temperature of 160° C. or higher inthe presence of an equal weight or less of phenol and 20 mol % or lessof sulfuric acid relative to the 4,4′-dihydroxydiphenylsulfone.
 2. Aprocess for producing a mixture of dihydroxydiphenylsulfone isomerscontaining 2,4′-dihydroxydiphenylsulfone, the process comprising heatinga mixture of dihydroxydiphenylsulfone isomers containing4,4′-dihydroxydiphenylsulfone in a proportion of at least 85 wt. % to atemperature of 160° C. or higher in the presence of an equal weight orless of phenol and 20 mol % or less of sulfuric acid relative to themixture.
 3. A process for producing a mixture ofdihydroxydiphenylsulfone isomers containing2,4′-dihydroxydiphenylsulfone, the process comprising heating4,4′-dihydroxydiphenylsulfone in the presence of phenol and sulfonicacid.
 4. A process for producing a mixture of dihydroxydiphenylsulfoneisomers containing 2,4′-dihydroxydiphenylsulfone, the process comprisingheating a mixture of dihydroxydiphenylsulfone isomers containing4,4′-dihydroxydiphenylsulfone in a proportion of at least 85 wt. % inthe presence of phenol and sulfonic acid.
 5. A process for producing amixture of dihydroxydiphenylsulfone isomers containing2,4′-dihydroxydiphenylsulfone, comprising: providing, as a singlestarting material, 4,4′-dihydroxydiphenylsulfone or a mixture ofdihydroxydiphenylsulfone isomers containing4,4′-dihydroxydiphenylsulfone in a proportion of at least 85 wt. %; andheating the starting material to a temperature of 160° C. or higher inthe presence of phenol in an amount equal to or less than the startingmaterial by weight and sulfuric acid in an amount of 20 mol % or lessrelative to the starting material to isomerize the starting material,thereby obtaining a mixture of dihydroxydiphenylsulfone isomerscontaining 2,4′-dihydroxydiphenylsulfone.
 6. The process according toclaim 5, wherein the mixture of dihydroxydiphenylsulfone isomerscontains 2,4′-dihydroxydiphenylsulfone in an amount 15–30 wt. %.
 7. Theprocess according to claim 5, wherein the starting material is heated to170–210° C.